HIV-infected patients are characterized for the presence or absence of neuropathy at [AS PER AMENDMENT 03/05/02: screening], baseline, Week 24, and Week 48. Entry variables are analyzed to determine predictors of progression from asymptomatic to symptomatic neuropathy or for worsening of symptomatic neuropathy. HIV-uninfected control volunteers have 1 visit [AS PER AMENDMENT 03/05/02: or 2 visits] for nerve conduction and Quantitative Sensory Testing (QST) evaluations to demonstrate proficiency with the testing methods prior to the enrollment of HIV-infected patients. HIV-infected patients are evaluated with the components of the Total Neuropathy Score (TNS) which includes signs (motor function, sensory function, and reflexes), symptoms (motor symptoms and sensory symptoms), QST (CASE IV - vibratory, cooling, and heat pain thresholds), and nerve conduction studies (sural nerve and peroneal nerve). Other evaluations include the Gracely Pain Scale and Visual Analog Scale pain diaries, paired skin biopsies from the right thigh and distal leg (total of 2), and peripheral blood lymphocyte analysis for quantitation of mitochondrial DNA content at entry and final study visit.